Low temperature properties of soft magnetic materials: magnetic viscosity and 1/f thermal noise

The characteristics of soft ferromagnetic cores at temperatures less than or equal to 4.2 K in the low field linear regime were investigated. The results showed that both high and near zero magnetorestrictive alloys emitted thermal magnetic noise of 1/f spectral density. Magnetic viscosity was also observed but it was not affected by the temperature. This behavior was thought to be brought about by thermally activated processes and quantum tunneling effects.